Electrical relay



' Feb. 16, 1943.

R. M. GILSON ELECTRICAL RELAY Filed May 17, 1940 I l I I Fig. 2.

227mm Bail/ Fig.4.

l NTOR Robe .Gimn BY nTTORNEY Patented Feb. 16, 1943 UNITED STATESPATENT OFFICE ELECTRICAL RELAY Application May 17, 1940, Serial No.335,781

9 Claims.

My invention relates to electrical relays, and it has particularreference to the provision of improved forms of relays of the classemployed in direct current railway track circuits.

An electrical relay of ordinary construction when employed as a trackrelay is relatively quick in picking up, is comparatively slow inreleasing, and may be subject to undesirable operations due to momentarylosses of train shunt in its associated section. These characteristicsare in a large measure due to the fact that the energy required to pickup the armature of an ordinary relay is considerably in excess of theenergy necessary to hold such armature in its attracted position afterit has picked up. Such a relay must, of course, be designed to createits pick-up energy level, at least, in order to insure that the relayarmature will be picked up properly, and as a result once this armaturehas reached its attracted position, the energy level in the relay thenexceeds by a considerable degree that necessary to maintain the armaturein its picked-up position. In order for a train shunt to be effective torelease such relay, the shunt must be sufiiciently low in resistance toshunt away from the relay winding the increment of energy above thedrop-away energy level of the relay. Such shunt, however, provides a lowresistance or short-circuit path across the relay winding whichmaintains for an appreciable interval of time the flux in the relay, sothat a correspondingly long time interval is required for even a lowresistance train shunt to lower the energy level of the relay below itsdrop-away value. Hence, if the train shunt varies intermittently ineffectiveness, the release period of the relay might be materiallyincreased; and after the relay releases due to a shunt, there is apossibility that these variations in shunt might cause the relay to bepicked up and released and thus follow the fluctuations in the appliedshunt. This tendency of an ordinary relay to follow varying trainshunts, and the slow releasing characteristics possessed by such relaywhen shunted, are undesirable in a track relay since such relays oftenare incorporated into signaling or control systems not only forcontrolling signal indications, but also for establishing directionalcontrol in accordance with the sequence in which the relays of two ormore successive sections are released, hence if a relay is improperlypicked up in response to a momentary loss of train shunt, or if therelay of a section vacated by a train picks up prior to the traincausing the release of the relay of the section in advance, an improperdirectional set-up might be established as well as causing flashingsignal indications, etc. Furthermore, such relays are often employed forelectrically locking signals and switches against operation, and if atrack relay is intermittently released and picked up due to a varyingtrain shunt in its section, the effectiveness of such locking ismaterially decreased.

I am aware that schemes have been proposed heretofore to condition atrack relay to create its pick-up energy level when it is released, andto reduce the energy level in the relay after it has picked up, therebyobtaining quick release of the relay. One of the most effective of suchschemes is to employ a secondary relay, which ordinarily is slow acting,controlled by the track or primary relay and in turn controlling therelease sensitivity of the track relay. Such systems commonly are termedprimary-secondary track relay combinations, and although they materiallyimprove the operation of track relays and track circuits, the use of twoindependent relays increases the initial and maintenance cost of suchtrack circuit arrangements to a considerable extent.

In view of the foregoing and other important considerations, it is inobject of my invention to provide a track relay having means forcontrolling its own release sensitivity in such manner that the relay isconditioned to create its proper pick-up energy level when released, andwhen picked up the energy leve1 in the relay is reduced to a value onlyslightly above that required to hold its armature in its attracted po--sition.

Another object of my invention is to provide a track relay wherein thefunctions of the two relays oi a primary-secondary relay combination areincorporated into a single relay structure.

A further object of my invention is the provision of relays particularlysuitable for use as track relays, and incorporating novel and improvedmeans for delaying the pick-up oi the armatures of such relays.

An additional object of my invention is the provision of safe, reliable,and relatively inexpensive means for obtaining in a single relay thebenefits and advantages of a primary-secondary relay combination.

Another object of my invention is the provision of novel and improvedforms of electrical relays having slow pick-up, fast releasecharacteristics.

objects and characteristic features of my invention which will becomereadily apparent from the following description, are attained inaccordance with my invention by inductively coupling to the operatingwinding of a track relay a retaining winding which opposes the action ofthe operating winding on the contacts operated by the relay armature,and by utilizing a make-before-break contact combination operated bysuch armature to control the energy level created by the operatingwinding. This coupling of the operating and retaining windings of therelay is effected in accordance with my invention in such manner thatthe decay of flux due to current in the operating winding is notaffected, but the growth of flux is prolonged to aid in providing therelay with quick release, slow pick-up characteristics. Various meansfor coupling the windings in the above-described manner are provided; incertain forms of my invention shortly to be described, the retainingwinding is coupled to the operating winding over a back contact operatedby the relay armature; and in other forms of my invention the retainingwinding is coupled to the operating winding through an asymmetrical unitor through a fullwave rectifier.

The present invention is somewhat similar to that disclosed in acopending application, Serial No. 395,925, filed on May 31, 1941, byArthur E. Dodd, and which said copending application contains claimswhich cover broadly certain features of the invention described in mypresent application.

I shall describe four forms of electrical relays embodying my invention,and shall then point out the novel features thereof in claims.

In the accompanying drawing, Fig. 1 is a diagrammatic view showing apreferred form of an electrical relay embodying my invention, andincorporated into a railway track circuit. Figs. 2, 3 and 4 arediagrammatic views each illustrating a modified form of the relay shownin Fig. l, and each also embodying my invention.

In each of the several views of the drawing, similar referencecharacters have been employed to designate corresponding parts.

Referring first to Fig. 1, the reference character'TR designates, as awhole, a relay embodying my invention. As shown, this relay comprises anelectromagnet having two magnetizable cores 5' and 6 connected togetherat one end by a back strap 1. These cores are provided with an operatingor primary winding comprising two coils 8 and 8a disposed one on eachcore and connected in series in such manner that when energized thecoils cooperate in circulating a flux in agreement in the magneticcircuit of the relay. The cores 5 and 6 also carry a secondary windingcomprising two coils 9 and 9a, one coil 9 being disposed on core 5 andthe' other coil 90. being disposed on core 6. An armature l0, pivoted inthe usual manner (see Fig. 4), is disposed in magnetic relationship withthe two cores 5 and 6 and is operated from a released position (see Fig.2) to an attracted or pickedupposition (see Fig. 1) when coils 8 and 8aare energized. Armature It) is connected in the usual manner (not shown)to a plurality of contact members II, l2 and [3, which members engageassociated contact fingers to form front or back contacts according asarmature It is picked up or released. In addition, another contactmember I4' is operatively connected to armature l0 make-before-breakcontact arrangement. This contact arrangement, as shown, comprises amovable contact element I5 pivoted at [6 and provided with a frontcontact point I! and a button i3 of insulating material. The operationof the make-before-break contact arrangement will be explained in detailhereinafter, but at this time it should be pointed out that element I5preferably is restrained by any suitable means, such as by frictionwashers, to remain in its last operated position until acted upon bycontact member I4 attached to armature H].

An auxiliary magnetizable core 29 disposed beneath armature It isengaged by the armature in its released position (see Fig. 2) and thiscore carries a retaining winding 21 which is effective when energized tocreate magnetic flux which tends to hold armature H3 in its releasedposition, thus opposing the action on armature ll] of the flux due tocurrent in coils 8 and 8a. Winding 21 is supplied with current at timesfrom the two secondary winding coils 9 and 9a disposedon the two maincores 5 and 6, these coils being connected in series in such manner thatwhen electromotive forces are induced therein due to a change inmagnetic conditions in the cores 5 and 6, such forces are additive. Inthe embodiment of my invention illustrated in Fig. 1, the two coils 9,9a of the secondary winding are connected to retaining winding 2| over aback contact |l--22 closed in the released position of armature H0; in asecond embodiment of my invention illustrated in Fig. 2, the two coils9, 9a are connected through back contact H-22 of' relay TRI to the inputterminals of a full-wave rectifier R (see Fig. 2), and the outputterminals of this rectifier are connected to winding 2!; and in anotherembodiment of my invention illustrated in Fig. 3 an asymmetrical unit 23(see Fig. 3) is interposed in the connection of coils 9 and 9a. of relayTR2 to winding 2|.

As shown in Fig. 1, relay TR is connected in a track circuit includingthe two track rails l and la of a section of railway track D-E, whichsection is formed by insulating the track rail portions of section D-Efrom the adjacent portions of such rails through the medium of thecustomary insulated joints 2. The track circuit also includes, as shown,a suitable source of current,

2 such as a track battery TB, connected in series with the usual currentlimiting resistor 3, across the rails I and la at one end E of thesection, and at times only a portion and at other times the entireoperating winding of relay TR. connected in series with a currentlimiting resistor and controls what I shall term a drag or a 4 acrossthe track rails I and la at the other end D of the section.

The operation of the apparatus illustrated in Fig. 1 is asfollows: Whensection D-E is unoccupied, armature Ii] of relay TR is in its attractedor upper position as shown in Fig. 1, and in this position of armaturein front contact l4- ll of relay TR is closed to complete an obviouscircuit path which connects coil 8 of relay TR across the rails I andla. The parts of relay TR preferably are designed and proportioned insuch manner that with only coil 8 energized, an energy level onlysufiiciently above the release value of the relay to assure reliableoperation of such relay under the various ballast conditions, is createdin the relay due to current supplied to the one coil 8 of the operatingwinding from the rails l and la.

When a train enters section D-E, the current supplied from battery TB tothe track rails I and l a is shunted away from the operating winding ofrelay TR. Since the relay armature normally is held attracted by anenergy level only slightly in excess of its release value, the energylevel in the relay is rapidly decreased by the applied shunt and as aresult armature it drops to its leased position wherein back contactfinger I9 is engaged by contact element l5 (see Fig. 2).

In the released position of armature ID of relay TR, back contact ||-22is closed to connect coils 9 and 9a of the secondary winding disposed oncores 5 and 6 to retaining winding 2|. Also, both coils 8 and 8a of theoperating Winding of relay TR are connected in series over back contact|5|9 across the track rails and la, thereby conditioning the relay tocreate its pick-up energy level. When the train shunt is removed fromrelay TR, as for example when the train vacates section D-E or when theshunt is'momentarily lost due to rail film conditions or other poorshunting conditions, current from battery TB is supplied through railsand la to both coils 8 and 8a of relay TR. During the building up'oi theflux in cores 5 and 6 due to such current, electromotive forces areinduced in the secondary winding coils 9 and 9a disposed on cores 5 and6. and are applied through back contact |i-22 to retaining winding 2|.The fiux set up due to current in winding 2| threads armature ID to holdthat armature down and thus opposes the action on armature ll! of theflux due to current in coils 8 and Ba. If the energization of the relayoperating winding is caused by the train vacating the section, theaction of winding 2| in opposing the pick-up effect of the flux due tocurrent in coils 8 and 8a functions to maintain armature H3 releaseduntil the flux condition in the cores 5 and 6 reaches substantially aconstant state condition so that no electromotive forces are induced incoils 9 and 9a. This steady state flux condition in the cores 5 and 6substantially corresponds to the pick-up energy level of the relay, andsince under the condition of flux equilibrium in cores 5 and 8 nocurrent is induced in the coils 9 and 9a, the tractive eiTect of theflux due to current in coils 8 and Ba on armature I0 is no longeropposed by flux due to current in winding 2|, and as a result armatureI0 is operated to its picked-up position wherein contact members I2 andI3 engage their respective front contact points and back contact ||-22is opened to disconnect retaining winding 2| from coils 9 and 9a. Also,When armature l0 reaches substantially its full attracted position,contact member l4 engages its associated front contact point I! to formcircuit controlling contact |4--|'| and to operate contact element l5about its pivot 55 to a position wherein back contact |5-i9 is opened.The closing of front contact |4-|'| connects coil 8 in circuit with thetrack rails and Ia; and the opening of back contact |5--| 9 opens thecircuit path connecting coil 8a in series with coil across the trackrails. The armature of relay TR accordingly is held in its attractedposition by All virtue of the energization of coil 8 only of theoperating winding of relay TR, consequently the energy level of therelay is reduced to a value only slightly greater than the release valueof the relay, as was pointed out heretofore. Relay 'IR accordingly isslow to pick up when the train vacates its associated section, therebyenabling the train to shunt the relay of the section in advance andpermitting the advance track relay to be released to establish theproper directional set-up, signal control, looking, or other functionwherein it is required for proper operation that the advance relay bereleased prior to the rear relay picking up,

In the event that armature ID of relay TR is released so that both coils8 and 8a are connected in circuit with the track rails, and current issupplied from the rails and la to such coils due to a loss of shunt insection D=E, then retaining winding 2| is energized by current suppliedfrom secondary coils 9 and 9a during the building up of flux in cores 5and 6, and armature Ill is held down by the flux due to current inwinding 2|. This hold-down effect of winding 2| prevents relay TR frompicking up immediately on a loss of shunt, and provides a delayedpick-up period for relay TR sufiicient under normal conditions to enablethe train shunt to be restored and the coils 8 and So again to beshunted prior to armature it being attracted from its released to itspicked-up position. It can be seen, therefore, that the delayed responsecharacteristics of a relay of the class illustrated in Fig. 1 preventsfalse operation of the relay due to a momentary loss of train shunt inits associated section.

It should be noted that the contacts operated by contact member M ofrelay TR function as make-before-break contacts during the travel of therelay armature from its released to its picked-up position, that is,front contact |4-|'l is closed prior to back contact |5-|9 being opened.In addition, the control of these contacts effected during the travel ofarmature Hi from its released to its picked-up position is such thatfront contact M-ll is closed and back contact |5-|9 is opened only afterthe armature reaches substantially its full attracted position, andsince there is but a slight air gap between the cores 5 and 6 andarmature Hi When contact |5--|9 opens to remove coil 8a. from the trackcircuit, the reduced energy level created in the relay after contact |i|closes and con tact |5|9 opens, is efiective to maintain the armature inits picked-up position. On the re verse travel of the armature from itspicked-up to its released position, however, front contact i is firstopened and then back contact !5|9 is subsequently closed, the closure ofthe back contact being delayed until the armature reaches substantiallyits full released position. This delayed closure of contact |5|i|permits the armature to be separated from the relay cores by arelatively large air gap prior to contact iii-l9 closing to connect bothwindings 3 and 8a of the relay in the relay circuit, thereby insuringthat the relay will be conditioned to create its pick-up energy levelonly after the relay armature reaches substantially its full-releasedposition. This avoids any tendency of the relay armature to bere-attracted to its pickedup position due to interposing both primarycoils in the track circuit before the armature separates from the relaycores.

It should, of course, be understood that while the particularconstruction and arrangement of the drag or make-before-break contactarrangement operated by contact member I4 of relay TR. is to bepreferred for the reasons set forth in detail, such contact arrangementmay take the form of the usual make-before-break contact arrangementsuch as is shown in Fig. 4 and presently to be explained in detail.

In addition, it should be noted that the two secondary coils 9 and 9adisposed on relay cores 5 and 6 are open-circulated at all times exceptwhen back contact H22 of the relay is closed and it follows that whenarmature I is picked up, such coils cannot operate to delay the decay ofrelay flux such as might happen if the secondary coils were connected atall times in circuit with winding 2|.

I have represented in Fig. 2' a modified arrangement of the relay shownin Fig. 1, whereby further increased insurance against false operationby shunts of varying effectiveness is provided by interposing afull-wave rectifier R between the secondary coils 9 and 9a and retainingwinding 2! of relay TRI. Referring now to Fig. 2, one input terminal ofrectifier R is shown connected to coil 90,, the other input terminal ofrectifier R is connected to coil 9 through back contact I |-22 of relayTRI, and the output terminals of the rectifier are connected toretaining winding 2!. It is readily apparent, therefore, that whenarmature l!) of relay TRI is released so that back contact I l22 isclosed, winding 2! is supplied with unidirectional current fromrectifier R irrespective of the polarity of the induced current insecondary coils 9 and 911. That is to say, current of one relativepolarity is induced in coils 9 and 9a during the interval that the relayflux is building up in cores 5 and 6, and current of the other relativepolarity is induced in such coils when the flux in cores 5 and 6 isdecaying. When back contact |l-22 is closed to connect rectifier R tocoils 9 and So, it is obvious that rectifier R functions to supplycurrent of only one polarity to winding 2| even though the flux in cores5 and 6 might be increasing and decreasing by turns, and consequentlythe unidirectional flux threading armature ID in its released positiondue to this current in winding 2| functions to hold such armature downwhen the train shunt in the section varies intermittently due to varyingconditions of rail surface film, rust, etc, in the section. Accordingly,it can be seen that when the effectiveness of the train shunt variesintermittently, the armature of a relay constructed as illustrated inFig. 2 is held down in its released position due to the variations inthe relay flux, and increased assurance is provided against improperoperation of the relay due to train shunts of varying effectiveness insection D E. The relay shown in Fig. 2 of course functions to provideretardation in the pick-up of the relay armature, and to vary the energylevel of the relay from its pick-up to its hold-up value, in a mannercorresponding to that pointed out in detail in connection with relay TRillustrated in Fig, 1, and further detailed explanation of the operationof relay TRI is believed to be unnecessary.

Relay TEE, illustrated in Fig. 3, incorporates another modification ofthe relay illustrated in Fig. 1. In relay TR2, back contact I l22 ofrelay TB is replaced by an asymmetrical unit 23 (see Fig. 3), which unitis interposed between retaining winding 2! and secondary coils 9 and 9aand is poled in such manner that winding 2| is supplied with currentfrom coils 9 and to when and only when the growth of flux in cores 5 and6 causes current of one relative polarity to be induced in coils 9 and9a. Winding 2| accordingly is energized and functions to delay thepicking up of the armature of relay TR2 when current is supplied to theoperating winding of the relay due to a train vacating the section orwhen the train shunt is of intermittent eifectiveness in the section,but since asymmetrical unit 23 opposes the flow of current of thepolarity such as would be induced in coils 9 and 9a due to a decaying ofthe flux in cores 5 and S, such unit in effect functions as an openedcontact to prevent any short-circuiting action of the coils 9 and 9atending to prolong the decay of flux in the cores 5 and 8. It follows,therefore, that asymmetrical unit 23 functions to control theenergization of winding 2| in a manner substantially similar to thecontrol established over the corresponding winding of relay TR bycontact H22, in that the unit permits the energization of winding 2! toenable that winding to delay the picking up of armature l5, and alsoprevents the coils 9 and 9a from prolonging the decay of the relay fiux.

Another modification of the relay illustrated in Fig. 1 is showndiagrammatically in Fig. 4, wherein a relay TRS is shown in a sideelevational view to better illustrate the construction and arrangementof its parts. This relay is substantially similar to relay TR shown inFig. 1, and accordingly comprises two cores each having two coilsmounted thereon, although only one core 5 and the two coils 8 and 9 areillustrated in Fig. 4.

Relay TR3 of Fig. 4 is characterized by the provision of two armaturemembers iii and 26, pivoted respectively about points 25 and 2?. Onearmature I9 is disposed in magnetic relationship with the magnetizablecores of relay TR3, and the other armature 26 is disposed in magneticrelation with retaining winding 2 I. Armature I8 is connected through aspring coupling 28 to armature 25 and the armatures are spaced apart inany suitable manner, such for example as by a nonmagnetic member 29attached to armature I8 and engaging a face of armature 2G. Attached tothe latter armature are a plurality of contact members 3?], 3! and 32,one of which 32 is bifurcated and functions as the common or bridgingmember of a make-before-break contact arrangement. If desired, armatureIt] also may be provided in the usual manner with contact members (notshown).

In the normal condition of relay TBS, as shown in Fig. 4, both armaturesI9 and 25 are in their respective upper or attracted positions and frontcontacts 39-34 and 32-35 of armature 25 are closed, the latter contactfunctioning to connect only a portion of the operating winding of relayTR? in its energizing circuit. This portion is shown in Fig. 4 ascomprising the upper portion of winding 8 of relay TR3, which isconnected through a resistor 39 and front contact 3532 operated byarmature 25, to the indicated control circuit (which may be the trackcircuit represented in Fig. 1) but it is to be understood, or" course.that this showing is merely illustrative, and the upper portion ofwinding 8 of relay IE3 might correspond to the entire coil 8 of relay TRshown in Fig. 1, in which case the lower portion of winding 8 of relayTR3, which normally is excluded from the control circuit for the relay,would then correspond to coil Ba of relay TR shown in Fig. 1. The partsof relay 'IRt are so proportioned and designed that when only a selectedportion of the operatin winding is included over front contact .32-35 inthe control circuit of the relay, the

energy level created in the relay due to current in the included portionof such winding is only slightly in excess of the release value of therelay.

Accordingly, armature I is held in its picked-up position due to themagnetic flux in the relay cores, and armature 26 is held in itspicked-up position wherein it bears against stop 29 due to the action ofspring 28.

If relay TR3 is connected in circuit with the rails of a track section,for example, then a train shunt in the section reduces the energy levelin the relay and its armatures I0 and 26 drop. Back contacts 3236,3|--3| and 3938 are closed by the operation of armature 26 to itsreleased posicircuit with the track rails, thus conditioning the relayto create its pick-up energy level. When the shunt is removed, currentinduced in coil 9 due to the growth of flux in core 5 is supplied overback contact 3l--31 to winding 2 l, with the result that armature 26 isheld down by the flux due to the current in this winding. Armature Hi,however, is attracted to its upper position due to the flux in core 5,and when the armature closes the flux again increases due to thedecreased air gap to prolong the interval during which electrornotiveforces are induced in secondary winding 9 and are supplied to winding21. Armature 26 accordingly is held down due to current in winding 2|until the flux condition in core 5 reaches substantially a steady statecondition after armature l0 closes, and when this happens, the retainingaction of winding 2| ceases so that armature 26 is operated to its upperposition due to the action of its spring coupling 28. This movement ofarmature 26, of course, opens back contact 3l-3l to disconnect secondarywinding 9 from retaining winding 2 l, and also closes front contact32-35 prior to opening back contact 32-36, so that the upper portion ofwinding 8 is connected to the control circuit prior to opening theconnection of the entire control winding to such circuit.

From the foregoing, it can be seen that the construction of relay TR3 issuch that armature I0 is operated to its full attracted position priorto reducing the energization of the relay, and that the armature 26 isdelayed from responding to the energization of the relay operatingwinding during the building up of flux in the relay core due both to theenergization of the relay winding and the closing of armature [0. Itfollows, therefore, that an improved relay is provided having quickrelease, slow pick-up characteristics and incorporating means forvarying the energy level created in the relay after its armature hasreached its full attracted position.

Although I have herein shown and described only four forms of electricalrelays embodying my invention, it is understood that various changes andmodifications may be made therein within the scope of the appendedclaims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a magnetizable core, an operating winding disposed onsaid core, an armature disposed in magnetic relation to said core andprovided with contacts including a makebefore-break contact combinationcomprising a front contact and a back contact with a bridging memberwhich causes both said contacts to become closed momentarily during themovement of said armature from its released to its attracted position, acontrol circuit connected over said front contact to a portion only ofsaid operating winding and connected over said back contact to theentire operating winding, a retaining winding disposed to retain saidarmature in its released position in opposition to the attractive actionof said operating winding on said armature, and a secondary windingdisposed on said core and connected to said retaining winding through anasymmetrical unit poled in such manner as to permit only the flow ofcurrent caused to be induced in said secondary winding due to a growthof flux in said core.

2. In combination, a magnetizable core, an operating winding disposed onsaid core, an armature disposed in magnetic relation to said core andprovided with contacts including a make-beforebreak contact combinationcomprising a front contact and a back contact with a bridging memberwhich causes both said contacts to become closed momentarily during themovement of said armature from its released to its attracted position, acontrol circuit connected over said front contact to a portion only ofsaid operating winding and connected over said back contact to theentire operating winding, a retaining winding disposed to oppose theattractive action on said armature of said operating winding formaintaining said armature in its said released position, a

rectifier, and a secondary winding disposed on said core and connectedto said retaining winding through said rectifier.

3. In combination, a magnetizable core, an operating winding disposed onsaid core, an armature disposed in magnetic relation to said core andprovided with contacts including a make-beforebreak contact combinationcomprising a front contact and a back contact with a bridging memherwhich causes both said contacts to become closed momentarily during themovement of said armature from its released to its attracted position, acontrol circuit connected over said front contact to a portion only ofsaid operating winding and connected over said back contact to theentire operating winding, a rectifier, a retaining winding connected tothe output terminals of said rectifier and disposed to oppose theattractive action of said operating winding on said armature, and asecondary winding disposed on said core and connected through a backcontact of said armature to the input terminals of said rectifier.

4. In a relay, in combination, a magnetizable core and an armature, anoperating winding disposed on said core for actuating said armature,another magnetizable core disposed in effective magnetic relation withsaid armature when the latter is released, a retaining winding on saidother core, an asymmetrical unit, and a secondary winding disposed onsaid first core and connected to said retaining winding through saidasymmetrical unit, said unit being poled in such direction as to permitonly the flow of current induced in said secondary winding due to agrowth of flux in said first core.

5. In a relay, in combination, two magnetizable cores, an operatingwinding disposed on one of said cores, a contact-carrying armaturebiased to the other of said cores and actuated against its bias to saidone core in response to flux due to current in said operating winding, aretaining winding on said other core, an asymmetrical unit, and asecondary winding disposed on said one core and connected through saidasymmetrical unit to said retaining winding, said unit being poled insuch direction as to permit only the flow of current induced in saidsecondary winding due to the growth of flux in said one core.

6. In a relay, in combination, two magnetizable cores, an operatingwinding disposed on one of said cores, a contact-carrying armaturebiased to the other of said cores and actuated against its bias to saidone core in response to flux due to current in said operating winding, arectifier, a retaining winding disposed on said other core and connectedto the output terminals of said rectifier, and a. secondary windingdisposed on said one core and connected through a back contact of saidarmature to the input terminals of said rectifier.

'7. In combination, a relay comprising a magnetizable core and a firstarmature, an operating winding disposed on said core for actuating saidfirst armature, a second armature spring coupled to said first armature,contacts operated by said second armature, a retaining winding disposedto be effective when energized to retain said second armature in itsreleased position against the action of said spring coupling, and asecondary winding disposed on said core and connected to 'said retainingwinding when and only when said second armature is released.

8. In combination, a relay comprising a magnetizable core and a firstarmature, an operating winding disposed on said core for actuating saidarmature, a second armature spring coupled to said first armature, aplurality of contacts operated by said second armature and including amake-before-break contact combination comprising a back contact and afront contact with a bridging member which causes both said front andback contacts to become closed momentarily during a portion of theoperating stroke of said second armature, a control circuit connectedover said front contact to a portion of said operating winding andconnected over said back contact to the entire operating winding, aretaining winding disposed to be efiective when energized to oppose theaction of said spring coupling on said second armature, and a secondarywinding disposed on said core in inductive relation to said operatingwinding and connected to said retaining winding when said secondarmature is released.

9. In a relay, in combination, two magnetizable cores, an armaturebiased away from one toward the other of said cores, an operatingwinding on said one core for actuating said armature to said first core,a second armature spring coupled to said first armature and disposed inefiective magnetic relation With said second core, a retaining windingdisposed on said second core, and a secondary winding disposed on saidone core and connected to said retaining winding over a back contact ofsaid second armature.

ROBERT M. GILSON.

